Pacifastacus leniusculus (American signal crayfish)
- Summary of Invasiveness
- Taxonomic Tree
- Distribution Table
- History of Introduction and Spread
- Habitat List
- Natural Food Sources
- Water Tolerances
- Natural enemies
- Pathway Causes
- Pathway Vectors
- Impact Summary
- Environmental Impact
- Threatened Species
- Risk and Impact Factors
- Uses List
- Similarities to Other Species/Conditions
- Prevention and Control
- Links to Websites
- Distribution Maps
Don't need the entire report?
Generate a print friendly version containing only the sections you need.Generate report
PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Pacifastacus leniusculus Dana, 1852
Preferred Common Name
- American signal crayfish
International Common Names
- English: crawfish; North American signal crayfish; signal crayfish; signal crayfish, American
Local Common Names
- Czech Republic: rak signální
- Denmark: signalkrebs
- Estonia: signaalvähk
- Finland: täplärapu
- Germany: Signalkrebs
- Latvia: signalvezis
- Lithuania: žymetasis vežys
- Netherlands: Californische rivierkreeft
- Norway: signalkreps
- Poland: rak sygnalowy
Summary of InvasivenessTop of page
Native to western North America, Pacifastacus leniusculus, the American signal crayfish, is one of the top three most invasive crayfish species in the world and the most widespread non-native crayfish in Europe. It has been found in 28 territories in Europe since the 1960s, largely due to its high adaptability to a wide range of environments. P. leniusculus is now widely cultivated in Europe and has provided a culinary substitute following the decline of the native European species, Astacus astacus, from crayfish plague. In fact, its use for restocking crayfish plague-devastated European waters is the primary reason for its current wide distribution in Europe. Ironically, P. leniusculus, though resistant to crayfish plague, is a vector of the causal factor, and has been implicated in many plague outbreaks, which have seriously impacted native crayfish populations.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Arthropoda
- Subphylum: Crustacea
- Class: Malacostraca
- Subclass: Eumalacostraca
- Order: Decapoda
- Suborder: Reptantia
- Unknown: Astacoidea
- Family: Cambaridae
- Genus: Pacifastacus
- Species: Pacifastacus leniusculus
DescriptionTop of page
P. leniusculus has a smooth, reddish-brown exoskeleton and bright red undersides to the chelae. It has a white dorsal patch at the junction of the moveable and fixed finger of the chela (Lewis, 2002). Male crayfish can reach a length of 16 cm, while females can only achieve a maximum size of 12 cm. Age at maturity varies from 1 to 3 years, and a life expectancy of up to 20 years is possible.
DistributionTop of page
P. leniusculus is distributed from British Columbia in Canada at the northern part of its range, south to central California and east to Utah and Montana in the USA. In the 1960s, P. leniusculus was introduced into Europe and now occurs in many countries from the UK and France in the west, to Russia in the east. A population near Inverness, Scotland constitutes the limit of the species range in the northwest; the northern extent is Norway, Sweden and Finland, while the southern extent is the Iberian Peninsula. There are also satellite populations in Greece and Cyprus. P. leniusculus has also been introduced outside of Europe, to Japan (Hiruta, 1996).
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.Last updated: 10 Jan 2020
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|United States||Present||Present based on regional distribution.|
IntroductionsTop of page
|Introduced to||Introduced from||Year||Reason||Introduced by||Established in wild through||References||Notes|
|Natural reproduction||Continuous restocking|
|Japan||Aquaculture (pathway cause)||Unknown||No||No||Hiruta (1996)|
|Sweden||California||1959||Aquaculture (pathway cause)||Private sector||Yes||No||Fürst (1977)|
|UK||Sweden||1976||Aquaculture (pathway cause)||Unknown||Yes||No||Hogger (1986)|
HabitatTop of page
P. leniusculus can be found in a variety of habitats, from small streams to large rivers and natural lakes. It is also known to occur in brackish waters along the Pacific Coast in salinities as high as 20 ppt (Riegel, 1959). Its ability to tolerate water temperatures up to 33°C has allowed it to prosper in many environments.
Habitat ListTop of page
|Freshwater/Lakes||Present, no further details||Harmful (pest or invasive)|
|Freshwater/Rivers / streams||Present, no further details||Harmful (pest or invasive)|
|Freshwater/Lakes||Present, no further details||Natural|
|Freshwater/Rivers / streams||Present, no further details||Natural|
Natural Food SourcesTop of page
|Food Source||Food Source Datasheet||Life Stage||Contribution to Total Food Intake (%)||Details|
|Aquatic insects (Ephemeroptera, Chironomidae, Coleoptera, Plecoptera, Trichoptera and Diptera)||Adult/Fry|
|Plant material (alder, maple leaves)||Adult|
ClimateTop of page
|C - Temperate/Mesothermal climate||Preferred||Average temp. of coldest month > 0°C and < 18°C, mean warmest month > 10°C|
Water TolerancesTop of page
|Parameter||Minimum Value||Maximum Value||Typical Value||Status||Life Stage||Notes|
|Water temperature (ºC temperature)||15||23||Optimum||Adult|
Natural enemiesTop of page
|Natural enemy||Type||Life stages||Specificity||References||Biological control in||Biological control on|
|Alcedo atthis||Predator||Adult||Hogger (1988)|
|Anguilla anguilla||Predator||Adults||Blake and Hart (1995)|
|Ardea cinerea||Predator||Adult||Hogger (1988)|
|Lutra lutra||Predator||Adult||Hogger (1988)|
|Micropterus dolomieu||Predator||Adult||Pflug and Pauley (1984)|
|Neovison vison||Predator||Adult||Hogger (1988)|
|Perca fluviatilis||Predator||Adult||Appelberg and Odelstrom (1987); Soderback (1994)|
|Procyon lotor||Predator||Adult||Hogger (1988)|
|Prosopium williamsoni||Predator||Adult||Lewis (1999)|
|Ptychocheilus oregonensis||Predator||Adult||Jeppson and Platts (1958)|
|Salmo trutta||Predator||Adult||Lewis (1999)|
|Silurus glanis||Predator||not specific|
Pathway CausesTop of page
Pathway VectorsTop of page
Impact SummaryTop of page
|Fisheries / aquaculture||Positive|
Environmental ImpactTop of page
The introduction of P. leniusculus has had negative impacts on native crayfish populations globally. Native crayfish species are frequently replaced due to having lower fecundities (Eng and Daniels, 1982), an inferior ability to compete for shelter leading to an increased susceptibility to predation (Dunn et al., 2009), vulnerability to reproductive interference leading to diminished recruitment (Westman et al., 2002) or due to being directly predated upon (Nataka and Goshima, 2006). The spread of P. leniusculus throughout Europe has enabled Aphanomyces astaci, the crayfish plague, to spread as well, decimating native crayfish populations (Holdich et al., 2009).
P. leniusculus presence in the River Clyde, Scotland, was associated with a 40% reduction in benthic invertebrate density compared to P. leniusculus absence, with an associated reduction in species diversity (Crawford et al., 2006). This impact on macroinvertebrate communities was alleviated by intensive removal of signal crayfish using traps (Moorhouse et al., 2014). In two similar rivers in Yorkshire (UK), high P. leniusculus densities correlated with low salmonid fish densities (brown trout, Salmo trutta), whilst high native white-clawed crayfish, Austropotamobius pallipes, densities correlated with high fish densities, suggesting a population level impact of P. leniusculus on fish communities (Peay et al., 2009). Melero et al. (2014) have also demonstrated an increased density and resilience to control of invasive non-native mammalian carnivore populations such as the American mink, Neovison vison, in ecosystems with established invasive non-native crayfish populations, due the availability of a superabundant prey item.
The burrows of signal crayfish lead to bank erosion and increased fluvial sediment mobilisation, which could eventually contribute to bank collapse (Harvey et al., 2011).
For further impacts see Johnsen and Taugbøl (2010).
Threatened SpeciesTop of page
|Threatened Species||Conservation Status||Where Threatened||Mechanism||References||Notes|
|Austropotamobius pallipes (freshwater white-clawed crayfish)||EN (IUCN red list: Endangered)|
|Pacifastacus fortis (Shasta crayfish)||CR (IUCN red list: Critically endangered); USA ESA listing as endangered species||California||Competition - monopolizing resources; Predation||US Fish and Wildlife Service (2009)|
Risk and Impact FactorsTop of page
- Proved invasive outside its native range
- Has a broad native range
- Abundant in its native range
- Highly adaptable to different environments
- Is a habitat generalist
- Capable of securing and ingesting a wide range of food
- Highly mobile locally
- Modification of natural benthic communities
- Reduced native biodiversity
- Threat to/ loss of native species
- Competition - monopolizing resources
- Competition (unspecified)
- Pest and disease transmission
- Highly likely to be transported internationally deliberately
- Difficult/costly to control
Uses ListTop of page
Animal feed, fodder, forage
Human food and beverage
- Fresh meat
- Live product for human consumption
Similarities to Other Species/ConditionsTop of page
P. leniusculus is similar in appearance to the noble crayfish, Astacus astacus. The main difference is the presence in P. leniusculus of the white dorsal patch at the junction of the moveable and fixed finger of the chela (Lewis, 2002). P. leniusculus also lacks the spine on each side of the carapace which is present in A. astacus. For more information see section on species identification in Johnsen and Taugbøl (2010).
Prevention and ControlTop of page
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
For information on this, see Stebbing et al. (2014).
ReferencesTop of page
Ackefors H, Lindqvist OV, 1994. Cultivation of freshwater crayfishes in Europe. In: Huner JV, ed. Freshwater Crayfish Aquaculture. New York, USA: Haworth Press, 157-216
Appelberg M, Odelstrom T, 1987. Interaction between European perch (Perca fluviatilis) and juvenile Pacifastacus leniusculus (Dana) in a pond experiemnt. Freshwater Crayfish, 7:37-45
Bernardo, J. M., Costa, A. M., Bruxelas, S., Teixeira, A., 2011. Dispersal and coexistence of two non-native crayfish species (Pacifastacus leniusculus and Procambarus clarkii) in NE Portugal over a 10-year period. Knowledge and Management of Aquatic Ecosystems, 401(28), 1-13. doi: 10.1051/kmae/2011047
Blake MA, Hart PJB, 1995. The vulnerability of juvenile signal crayfish to perch and eel predation. Freshwater Biology, 33, 233-244.
Crawford, L., Yeomans, W. E., Adams, C. E., 2006. The impact of introduced signal crayfish Pacifastacus leniusculus on stream invertebrate communities. Aquatic Conservation: Marine and Freshwater Ecosystems, 16(6), 611-621. http://www3.interscience.wiley.com/cgi-bin/abstract/112597211/ABSTRACT doi: 10.1002/aqc.761
Dunn, J. C., McClymont, H. E., Christmas, M., Dunn, A. M., 2009. Competition and parasitism in the native white clawed crayfish Austropotamobius pallipes and the invasive signal crayfish Pacifastacus leniusculus in the UK. Biological Invasions, 11(2), 315. http://www.springerlink.com/content/9095w4r00p035l7j/?p=0c1a2f95bea14a67a6d603f344c29c3b&pi=14 doi: 10.1007/s10530-008-9249-7
Eng LL, Daniels RA, 1982. Life history, distribution and status of Pacifastacus fortis (Decapoda: Astacidae). California Fish and Game, 68(4):197-212
Fürst M, 1977. Introduction of Pacifastacus leniusculus (Dana) into Sweden: methods, results and management. Freshwater Crayfish, 3, 229-247.
Gonzalez J, Carral JM, Celada JD, Sáez-Royuela M, Gaudioso VR, Fernández R, López-Baissón C, 1993. Management of crayfish eggs (Pacifastacus leniusculus) for intensification of juvenile production. Freshwater Crayfish, 9:144-146
Harvey, G. L., Moorhouse, T. P., Clifford, N. J., Henshaw, A. J., Johnson, M. F., Macdonald, D. W., Reid, I., Rice, S. P., 2011. Evaluating the role of invasive aquatic species as drivers of fine sediment-related river management problems: the case of the signal crayfish (Pacifastacus leniusculus). Progress in Physical Geography, 35(4), 517-533. http://ppg.sagepub.com/ doi: 10.1177/0309133311409092
Hiruta S, 1996. The presence of signal crayfish in Hokkaido, Japan. Crayfish News, 19:1
Hogger JB, 1986. Aspects of the introduction of “signal crayfish”, Pacifastacus leniusculus (Dana), into the Southern United Kingdom. 1. Growth and survival. Aquaculture, 58(1-2), 27-44.
Hogger JB, 1988. Ecology, population biology, and behaviour. In: Holdich DM, Lowery RS, eds. Freshwater Crayfish. Biology, Management and Exploitation. London, Portland: Croom Helm Ltd., 114-144, 424-479
Holdich, D. M., Reynolds, J. D., Souty-Grosset, C., Sibley, P. J., 2009. A review of the ever increasing threat to European crayfish from non-indigenous crayfish species. Knowledge and Management of Aquatic Ecosystems, (No.394/395), 11. http://www.kmae-journal.org/articles/kmae/pdf/2009/03/kmae09055.pdf doi: 10.1051/kmae/2009025
Jeppson PW, Platts WS, 1958. Ecology andcontrol of the Columbia squawfish in Northern Idaho lakes. Transactions of the American Fisheries Society, 88:197-202
Johnsen SI, Taugbøl T, 2010. Pacifastacus leniusculus. NOBANIS Invasive Alien Species Fact Sheet. Online Database of the North European and Baltic Network on Invasive Alien Species - NOBANIS. http://www.nobanis.org
Jussila J, Hytinen L, Lahti E, Pulkkinen V, 1990. Mikkelin laaninraputalouden elvytyssuunnitelma vuosille 1990-95. Mikkelin kalastuspiirin julkaisu nro 4
Jussila J, Mannonen A, 1995. Crayfish culture in Finland, Northern Europe. Marron Grower’s Bulletin, 17(1):2-6
Kouba A, Petrusek A, Kozák P, 2014. Continental-wide distribution of crayfish species in Europe: update and maps. Knowledge and Management of Aquatic Ecosystems, 413(5), 1-31.
Larson ER, Olden JD, 2011. The state of crayfish in the Pacific Northwest. Fisheries, 36(2), 60-73.
Lewis SD, 1999. Abundance, activity and diet of littoral fish in Lake Billy Chinook, Lake Simtustus and Reregulating Reservoir, Oregon, 1997-1999. Portland General Electric Company, Portland, Oregon, USA
Melero, Y., Palazón, S., Lambin, X., 2014. Invasive crayfish reduce food limitation of alien American mink and increase their resilience to control. Oecologia, 174(2), 427-434. http://link.springer.com/article/10.1007%2Fs00442-013-2774-9 doi: 10.1007/s00442-013-2774-9
Moorhouse, T. P., Poole, A. E., Evans, L. C., Bradley, D. C., Macdonald, D. W., 2014. Intensive removal of signal crayfish (Pacifastacus leniusculus) from rivers increases numbers and taxon richness of macroinvertebrate species. Ecology and Evolution, 4(4), 494-504. http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)2045-7758 doi: 10.1002/ece3.903
Nakata K, Goshima S, 2006. Asymmetry in mutual predation between the endangered Japanese native crayfish Cambariodes japonicus and the North American invasive crayfish Pacifastacus leniusculus: a possible reason for species replacement. Journal of Crustacean Biology, 26(2), 134-140.
Nylund V, Westman K, 1981. Frequency of visible symptoms of the crayfish plague fungus (Aphanomyces astaci) on the American crayfish (Pacifastacus leniusculus) in natural populations in Finland. Freshwater Crayfish, 5:277-283
Pârvulescu, L., Schrimpf, A., Kozubíková, E., Resino, S. C., Vr?lstad, T., Petrusek, A., Schulz, R., 2012. Invasive crayfish and crayfish plague on the move: first detection of the plague agent Aphanomyces astaci in the Romanian Danube. Diseases of Aquatic Organisms, 98(1), 85-94. http://www.int-res.com/abstracts/dao/v98/n1/p85-94/ doi: 10.3354/dao02432
Peay, S., Guthrie, N., Spees, J., Nilsson, E., Bradley, P., 2009. The impact of signal crayfish (Pacifastacus leniusculus) on the recruitment of salmonid fish in a headwater stream in Yorkshire, England. Knowledge and Management of Aquatic Ecosystems, (No.394/395), 12. http://www.kmae-journal.org/articles/kmae/pdf/2009/03/kmae09022.pdf doi: 10.1051/kmae/2010003
Pflug DE, Pauley GB, 1984. Biology of smallmouth bass (Micropterus dolomieui) in Lake Sammanish, Washington. Northwest Science, 58(2):118-130
Riegel JA, 1959. The systematics and distribution of crayfish in California. California Fish and Game, 45:29-50
Skov, C., Aarestrup, K., Sivebæk, F., Pedersen, S., Vr?lstad, T., Berg, S., 2011. Non-indigenous signal crayfish Pacifastacus leniusculus are now common in Danish streams: preliminary status for national distribution and protective actions. Biological Invasions, 13(6), 1269-1274. http://www.springerlink.com/content/m751771l68345507/ doi: 10.1007/s10530-010-9901-x
Soderback B, 1994. Interactions among juveniles of two freshwater crayfish species and a predatory fish. Oecologia, 100:229-235
Stebbing, P., Longshaw, M., Scott, A., 2014. Review of methods for the management of non-indigenous crayfish, with particular reference to Great Britain. Ethology Ecology & Evolution, 26(2/3), 204-231. http://www.tandfonline.com/loi/teee20
United States Geological Survey, 2011. Pacifastacus leniusculus. USGS Nonindigenous Aquatic Species Database. Gainesville, Florida, USA: USGS. http://nas.usgs.gov/queries/factsheet.aspx?SpeciesID=200
US Fish and Wildlife Service, 2009. Shasta crayfish, Pacifastacus fortis, 5-year review: Summary and evalution. In: Shasta crayfish, Pacifastacus fortis, 5-year review: summary and evalution : US Fish and Wildlife Service.22 pp.
Westman K, Pursiainen M, Westman P, eds, 1990. The situation of crayfish stocks, fisheries, diseases and crayfish culture in Europe - a review. In: Status of Crayfish Stocks, Fisheries, Diseases and Culture in Europe, pp. 5-31. Report of the FAO European Inland Fisheries Advisory Commission (EIFAC) Working Party of Crayfish, Helsinki, FInland
Westman, K., Savolainen, R., Julkunen, M., 2002. Replacement of the native crayfish Astacus astacus by the introduced species Pacifastacus leniusculus in a small, enclosed Finnish lake: a 30-year study. Ecography, 25(1), 53-73. doi: 10.1034/j.1600-0587.2002.250107.x
Wolf YS, 2004. Growth and macronutrient requirements of signal crayfish Pacifastacus leniusculus (Dana). PhD thesis. Germany: Christian Albrecht Universitat Kiel. Online at http://e-diss.uni-kiel.de/diss_1154/d1154.pdf. Accessed 23 September 2004
Bernardo J M, Costa A M, Bruxelas S, Teixeira A, 2011. Dispersal and coexistence of two non-native crayfish species (Pacifastacus leniusculus and Procambarus clarkii) in NE Portugal over a 10-year period. Knowledge and Management of Aquatic Ecosystems. 28-28fr. http://www.kmae-journal.org/index.php?option=com_article&access=standard&Itemid=129&url=/articles/kmae/abs/2011/02/kmae110033/kmae110033.html DOI:10.1051/kmae/2011047
CABI, Undated. CABI Compendium: Status inferred from regional distribution. Wallingford, UK: CABI
Hiruta S, 1996. The presence of signal crayfish in Hokkaido, Japan. In: Crayfish News, 19 1.
Johnsen SI, Taugbøl T, 2010. Pacifastacus leniusculus. In: NOBANIS Invasive Alien Species Fact Sheet, Online Database of the European Network on Invasive Alien Species – NOBANIS. 9 pp. http://www.nobanis.org
Kouba A, Petrusek A, Kozák P, 2014. Continental-wide distribution of crayfish species in Europe: update and maps. In: Knowledge and Management of Aquatic Ecosystems, 413 (5) 1-31.
Larson ER, Olden JD, 2011. The state of crayfish in the Pacific Northwest., 36 60-73.
Pârvulescu L, Schrimpf A, Kozubíková E, Resino S C, Vrǻlstad T, Petrusek A, Schulz R, 2012. Invasive crayfish and crayfish plague on the move: first detection of the plague agent Aphanomyces astaci in the Romanian Danube. Diseases of Aquatic Organisms. 98 (1), 85-94. http://www.int-res.com/abstracts/dao/v98/n1/p85-94/ DOI:10.3354/dao02432
Skov C, Aarestrup K, Sivebæk F, Pedersen S, Vrǻlstad T, Berg S, 2011. Non-indigenous signal crayfish Pacifastacus leniusculus are now common in Danish streams: preliminary status for national distribution and protective actions. Biological Invasions. 13 (6), 1269-1274. http://www.springerlink.com/content/m751771l68345507/ DOI:10.1007/s10530-010-9901-x
United States Geological Survey, 2011. (Pacifastacus leniusculus). In: USGS Nonindigenous Aquatic Species Database, Gainesville, Florida, USA: USGS. http://nas.usgs.gov/queries/factsheet.aspx?SpeciesID=200
ContributorsTop of page
27/06/14 Updated by:
Rupert Houghton, School of Biological Sciences, University of Aberdeen, UK
27/09/04 Original text by:
Uma Sabapathy Allen, Human Sciences, CAB International, Wallingford, Oxon, OX10 8DE, UK
Distribution MapsTop of page
Select a dataset
CABI Summary Records
Unsupported Web Browser:
One or more of the features that are needed to show you the maps functionality are not available in the web browser that you are using.
Please consider upgrading your browser to the latest version or installing a new browser.
More information about modern web browsers can be found at http://browsehappy.com/